EDIT: Hmmm....No idea why this ended up here; it was a response to the thread about a diode on the back of an alternator.....
If you're right, and it is a transorb, then you need to ask yourself why it's blown up. If the alternator went into overvoltage, it would have blown. If the battery was ever hooked up backward, it would have blown.
Note that if installed in a properly configured system (definitely *not* the case in that picture), the transorb (or a zener diode, for that matter) would not blow; the fuse/breaker that's (should be) upstream would blow/trip.
See the data sheet on the Spruce link for proper configuration. It isn't intended to protect the B lead circuit of the alternator, and cannot actually protect anything wired as shown in your pic.
Last edited by rv7charlie : 07-04-2017 at 06:48 PM.